The invention relates to a continuously operating rotational bottle filling device.
So called PET bottles (polyethyleneterephthalate), which have relatively thick-walled collars near their openings but have walls and bottoms that are thin, are being used to an ever increasing degree to contain beverages. When these bottles are put in a filling machine having support surfaces that raise and lower, it often happens that excessive axial pressure occurs when the bottle is applied against the filling unit, and this pressure is not withstood by the walls of the bottles.
Bottle filling devices have therefore been developed which, instead of having supporting surfaces for the bottoms of the bottles, use a gripping device for lifting the bottle by stiff collars that surround the mouth of the bottle in order to avoid axial overload on the body of the bottles. DE-OS 35 06 250, (U.S. Pat. No. 4,616,684), for example, discloses a bottle filling installation with such gripping devices which are respectively fastened to a vertically movable carriage that mounts to the rotating liquid storage tank. The track for the carriage is then supported externally of the valve body of the filling unit and is rigidly attached at its lower end to the U-shaped gripping device used for engaging the bottle collar. In order to bring about the application force by which the opening of the bottle is pressed against the seal of the filling unit so as to ensure filling that is problem-free when the bottle is in the filling position, this known installation features a pressure spring engaged between the fixed valve body and the movable carriage, said pressure spring acting upwards on the carriage. The carriages have rollers that are respectively raised or lowered at the intake and outlet of the filling installation by a fixed control cam. Since the pressure spring, which is under a minimum of tension when it is in the upper filling position, must nevertheless provide the required sealing force at the bottle mouth, the spring force increases greatly when the bottles are lowered, so that considerable spring force must be absorbed by the control cam or the carriage. This leads to signs of wear, particularly at the control cams. If, on the other hand, the pressure spring is replaced by a work cylinder in this known bottle filling installation, there is a danger of contaminating the filling units and the bottles by the escape of hydraulic oil or lubricating oil in the compressed air, so this solution is thus also not satisfactory.
From EP-OS 222 208 (U.S. Pat. No. 4,721,138) another bottle filling device of the type mentioned in the introduction is known, by which excessive loads on the control paths are avoided. For this purpose, a locking device is provided which locks the carriage into the upper filling position while the required application force for the bottle mouth is brought about by the fact that the filling unit with its sealing element rests on the liquid-containing tank and is vertically movable by means of a pressure spring. With this known bottle filling device the filling unit is raised against the pressure of the spring under tension during the last phase of the bottle-lifting motion, until the locking device locks the carriage. With this type of construction, therefore, a spring force results which only generates the required sealing force. But since the sealing element of the filling unit is arranged so as to be vertically movable under the liquid-containing tank, the clearance between the sealing element onto which the bottle opening is applied during filling and the seat of the liquid valve is relatively large, which, for reasons relating to filling technology, is a disadvantage. Additionally, the hollow spaces and the annular clearance within the sliding sleeve that bears the sealing element are difficult to clean.
The invention at hand is thus given the task of further improving a rotational bottle filling device of the type being considered, such that it completely satisfies the requirements relating to filling technology, and such that its mechanical construction is simple and sturdy.